1. Field of the Invention
The present invention relates to a method of and a system for pressing a sheet of glass into a highly curved sheet of glass which has a relatively small radius of curvature.
2. Description of the Prior Art
Some front and rear window glass sheets on automobiles are curved to relatively small radii of curvature. One known apparatus for bending a sheet of glass to a small radius of curvature is disclosed in Japanese Patent Publication No. 61(1986)-28611.
The disclosed apparatus has convex and concave molds for bending a glass sheet therebetween. The concave mold is composed of a central pressing mold member, and left and right pressing mold members. After the glass sheet is clamped between the central pressing mold member and the convex mold, the glass sheet is pressed to a curved shape between the central, left, and right mold members and the convex mold.
The convex mold and the concave mold, which is divided into the mold members, are however incapable of sufficiently stretching a central region of the glass sheet, so that the pressed glass sheet tends to have a insufficiently curved configuration. If the glass sheet were forcibly curved to correct insufficiently curved configuration, then the glass sheet would be liable to crack due to undue pressure. If the entire surface of the glass sheet were heated to high temperature, then a press mark would be left on the peripheral edges of the glass sheet by surface materials on the molds.
According to a solution disclosed in Japanese Patent Publication No. 61(1986)-17775, only the central region of a glass sheet is heated to a higher temperature than the other regions thereof, so that only the central region of the glass sheet can be curved to a greater degree. However, it has proven highly difficult to control the localized heating accurately.